Medical devices, such as implantable stents, have been used to deliver therapeutic agents directly to body tissue of a patient, particularly for treating restenosis. In particular, therapeutic agents can be incorporated into the medical device structure itself or incorporated into a coating that is disposed on the surface of the medical device.
In some instances it is desirable to increase the amount of therapeutic agent to be delivered by the medical device. However, the surface area of the medical device may limit the amount of therapeutic agent that can be delivered or incorporated into or onto the medical device. Thus, it may be desirable to have a medical device or a coating for a medical device with a greater surface area so that a greater amount of therapeutic agent can be incorporated into or onto the medical device.
Furthermore, in some instances, it is desirable to control the rate of release of the therapeutic agent from the medical device. For example, it may be desirable to have a constant rate of release of a therapeutic agent for an extended period of time. To ensure a constant rate of release, the amount of therapeutic agent that is loaded on to the implantable medical device must be above a certain amount and, at the same time, be able to be released from the medical device. In addition to ensuring an adequate amount of therapeutic agent is disposed on the medical device in order to achieve a constant release rate, it also desirable to prevent the therapeutic agent from being released from the medical device to the targeted tissue too rapidly, e.g., to avoid a burst effect.
Accordingly, there is a need for a medical device that can deliver the desired amount or dosage of a therapeutic agent. Furthermore, there is a need for a method of making a medical device with a greater surface area that can incorporate a desired amount of a therapeutic agent that will release from the medical device. Also, there is also a need for a medical device that can deliver the desired amount of a therapeutic agent at a desired rate or in a controlled manner over time.